Processes of chlorination of uranium oxides



United States Patent C PROCESSES OF CHLORINATION F URANIUM OXIDES SamRosenfeld, Los Angele's, Califi, assignor to the United States ofAmerica as represented by the United States Atomic Energy Commission NoDrawing. Application November 6, 1945 Serial No. 627,107

Claims. (Cl. 23-145) The present invention relates to processes ofproducing uranium tetrachloride through chlorination of uranium oxides,and more particularly to such processes using carbon tetrachloride andthe various oxides of uranium.

It is an object of the invention to provide an improved process ofproducing uranium tetrachloride of high chemical purity in crystallineform, wherein a majority of the product has a relatively largecrystalline grain size.

Another object of the invention is to provide an improved carbontetrachloride and uranium oxide process in which the vapor phasechlorination of a stationary uranium oxide charge may be effected morerapidly and completely than heretofore.

Another object of the invention is to provide an improvedcarbontetrachloride and uranium oxide process of producing uraniumtetrachloride which does not require agitation or rotation of the chargeto effect rapid and complete chlorination.

Another object of the invention is to provide an improved carbontetrachloride and uranium oxide process of producing uraniumtetrachloride in which a stationary uranium oxide charge is disposedwithin the chlorination zone to provide sufiicient surface for contactof the chlorinating agent to enable most rapid and completechlorination.

Another object of the invention is to provide a method for disposing auranium oxide charge within a vapor phase chlorinating zone so thatchlorination to produce uranium tetrachloride is efiected more rapidlyand completely than heretofore.

Still another object of the invention is to provide an improved processof producing uranium tetrachloride in which a stationary charge ofuranium oxide is disposed in thin layers in a reaction zone andcontacted with a chlorinating agent in the vapor phase, whereby rapidand complete chlorination to uranium tetrachloride is affected, and sidereactions productive of other uranium chlorides and other objectionablecompounds are minimized.

Still another object of the invention is to provide an improved processof producing uranium tetrachloride which employs reactions of a mixtureof carbon tetrachloride and phosgene with an oxide of uranium.

The invention both as to its organization and method of operationtogether with further objects and advantages thereof will best beunderstood by reference to the following specification.

In a copending application of James M. Carter, Serial No. 490,293, filedJune 10, 1943, which issued as Patent No. 2,677,592, on May 4, 1954,there is disclosed a process for the production of UCL, which employsreactions of a chlorinating agent such as CCL, with an oxide of uranium.In accordance with the process, a suitable charge of uranium oxide (U0U0 or U 0 is placed in a reaction chamber surrounded by a heater andheated to a reaction temperature, the interior of the reaction chambernear the charge being maintained at a temperaice ture within the range425 to 475 C. and as near 450 C. as practicable. Liquid CCL, isconducted through a conduit arranged adjacent the reaction chamber andsurrounded by the heater, whereby the CCL; is converted into the vaporphase and heated to a temperature of the order of 500 C. The hot CCL,vapor is then. conducted into the interior of the reaction chamber intodirect contact with the charge of uranium oxide, whereby the hot CCL;vapor reacts with the hot charge of uranium oxide to produce uraniumtetrachloride and certain reaction gases, including C0, C0 COCI and C1The reaction gases andthe unspent CCI, vapor are conducted from thereaction chamber through a suitable condenser, whereby the unspent CClvapor is condensed and the reaction gases are exhausted. Preferably, thecondensed CCL, is again conducted to the conduit for reconversion intothe vapor phase, whereby the unreacted C01,; is recycled repeatedly.

During the process, additional CCl is supplied as it is consumed in thereaction with the charge of uranium oxide, and the process is continueduntil all of the charge of uranium oxide has been converted into UCl Atthis time, when the reaction of the charge of uranium oxide is complete,the evolution of reaction gases ceases, thereby providing a readyindication of the completion of the process. Further, it is noted thatCOCl produced as a reaction gas is appreciably soluble in CCl wherebythe charge of uranium oxide is reacted with a mixture of (1C1, vapor andCOCl after the process is initiated. Thus, the COC1 also reacts with thecharge of uranium oxide to produce UC The fact that COCl reacts with thecharge of uranium oxide to produce UCL, is menifest by the consumptionof less than two moles of CCL, to produce one mol of UC1 as more clearlyindicated hereinafter.

Ordinarily, the process requires approximately four and one-half hoursto complete the reaction at the reaction temperature mentioned, wherebysubstantially all of the charge of uranium oxide is converted into UCL,and appears in crystalline form of dark green color.

While the process may be carried out at a reaction temperature below thelower end of the preferred range, at a temperature of 400 C., forexample, in order to produce UCh, this product so produced is in theform of a rather fine greenish colored powder and has a tendency to lumpvery badly. In addition, the reaction proceeds much more slowly.Similarly, while the process may be carried out at a reactiontemperature above the upper end of the preferred range, at a temperatureof 500 C., for example, in order to produce UCL, of the desiredcrystalline structure, the side reactions productive of other uraniumchlorides, such as UCl and various other objectionable compounds such asC Cl from breakdown of CCL, at this temperature are exceedinglyobjectionable in that the UCl escapes from the apparatus and clogs feedand exit lines; the product may be contaminated with UCl C Cl and othersubstances, and large amounts of CCL, are wasted. On the other hand,when the process is carried out at a reaction temperature within .thepreferred range, substantially complete conversion of the charge iseffected, and the product is of a very high chemical purity and of thedesired crystalline form. Also in this event, a minimum amount of CCl.,is utilized in the reaction and side reactions productive of otheruranium chlorides and other objectionable compounds are minimized. Thisproduct so produced, having the desired crystalline structure, isparticularly wellsuited for use in vacuum apparatus in which it may bevaporized or sublimed in carrying out other processes or methods, inthat the product being of relatively large crystalline structure may bereadily out-gassed, and has little tendency to be transported as dust inthe vacuum apparatus.

It is to be noted that in the course of carrying out the above, it isnecessary from time to time to rotate the charge or at least tap orshake the reaction chamber at suitable time intervals in order toprevent caking of the product and to cause the unreacted portion of thecharge to be presented to the surface of the mass to be contacted withreactant gases and reacted. In the absence of agitation, the reaction ofcarbon tetrachloride with uranium oxide penetrates only to a certaindepth beyond which a very hard cake would form.

'In accordance with the present invention, it has been 'found' that'ifit is desired "to maintain the charge stationary during the reaction,incomplete chlorination of the charge may be eliminated by disposing orspreading the uranium oxide charge in relatively thin layers on trays toprovde a large surface for contact of the chlorinating vapor. It hasbeen found that the most suitable product both as to quality andphysical form will be obtained When the depth of the charge in the trayis held between 0.1 and 0.5 cm. At no place within the trays should thecharge depth be more than 0.5 cm. and it is best to dispose the chargein a slight mound on the tray, thereby providing for less than a 0.5 cm.depth near its periphery. Thus, a minimum amount of CCL; is utilized inthe reaction and side reactions productive of other uranium chloridesand other objectionable compounds are minimized. The product so producedhas the most desirable crystalline structure. It is particularly wellsuited for use in vacuum apparatus in which it may be vaporized orsublimed in carrying out other processes or methods, in that theproduct, being of relatively large crystalline structure, may be readilyoutgassed and has little tendency to be transported as dust in thevacuum apparatus.

After UCl has been produced in accordance With the present process it isremoved from the reaction chamber into a dried container and maintainedunder a storage atmoshpere of CO Subsequently the product is transferredto a dry cabinet containing CO and screened in order to separateundesirable ends and a minor portion of the product in fine powderedform. The usable product is then bottled in an atmosphere of CO or in avacuum and sealed for future use in vacuum apparatus or otherwise as maybe desired. I It is pointed out that the oxide of uranium preferred as acharge in this reaction is U in that it has several advantages over theother oxides mentioned. A charge of U0 reacts much more readily than acharge of either U 0 or U0 a charge of U0 reacting most slowly of thethree uranium oxides mentioned. Also in U0 the uranium is already in thesame valence state as it is in the product UCl No chlorine is producedin the reaction and there is accordingly less tendency to form UCl andother objectionable compounds. Finally as a corollary of the fact that acharge of U0 is most rapidly converted this more rapid reaction isadvantageous in avoiding the formation of UCl and other objectionablecompounds as the reaction temperature can be kept towards the lower endof the preferred range.

While there has been described what is at present consider d to be thepreferred embodiment in the process, it will be understood that variousmodifications may be made therein and it is intended to cover in theappended claims all such modifications as fall within the true spiritand scope of the invention.

What is claimed is:

1. In the process comprising contacting carbon tetrachloride vapor withan oxide of uranium at a reaction temperature Within the range 425 to475 C., whereby uranium tetrachloride and reaction gases includingphosgenev are produced, condensing the unreacted carbon liquid carbontetrachloride and dissolved phosgene into in the reaction zone whereby amore complete and rapid:

4 1. o tetrachloride vapor, whereby carbon tetrachloride is sep; aratedthereby dissolving some of the phosgene from 5;, the remainder of thereaction gases, and reconverting the vapor to be contacted again withthe unreacted oxide of uranium, whereby the unreacted carbontetrachloride and some of the phosgene are recycled repeatedly and.maintaining the temperature within said range until the V oxide issubstantially completely converted to crystalline uranium tetrachloride,the major portion of the producthaving a crystalline size between 10 and60 mesh; improvement consisting of disposing the oxide of uraniu n'l'charge in trays within the reaction zone to a depth of tween 0.1 and 0.5centimeter whereby the reaction is rapidly and completely efiected.

2. In a large-scale process comprising reacting carbon tetrachloridevapor with an oxide of uranium at a rew tion temperature within therange 425 to 475 C., maintaining the temperature within said range untilthe] oxide is substantially completely converted to crystalline" uraniumtetrachloride, the major portion of the product having a crystal grainsize between 10 and 60 mesh; th improvement comprising disposing theoxide of uranium charge in expansive layers of 0.1 to 0.5 cm. inthickness reaction is efiected. 3. 'In a large-scale process comprisingreacting CC vapor with U0 at a reaction temperature within th range 425to 475 C.,. and maintaining the temperature within said range until theoxide is substantially complete-"E ly converted to crystalline UCl themajor portion of the product having a crystal grain size between 10andffiflf mesh; the improvement comprising disposing a large charge ofsaid U0 in open containers within a reaction; zone to a depth of between0.1 and 0.5 centimeter i expansive layers, whereby the reaction to formsaid crys talline UCl, is rapidly and completely elfected. 4. In alarge-scale process comprising reacting CCl vapor with U0 at a reactiontemperature within the] range 425 to 475 C., and maintaining thetemperature within said range until the oxide is substantially com-.1pletely converted to crystalline UCl the major portion of the producthaving a crystal grain size between 10 and 60 mesh; the improvementcomprising disposing a large charge of said U0 in trays within thereaction zone 0 to a depth of between 0.1 and0.5 centimeter inexpansive, layers, whereby the reaction to form said crystalline UCL, israpidly and completely eifected.

5. In a large-scale process comprising reacting CO1 vapor with U 0 at areaction temperature within the range 425 to 475 C., and maintaining thetemperaturef., within said range until the oxide is substantially cornpletely converted to crystalline U01 the major portion f ofthe producthaving a crystal grainv size between 10 and 60 mesh; the improvementcomprising disposing a large} charge of said U 0 in trays within thereaction zone to a depth of between -0.1 and 0.5 centimeter in expansivelayers, whereby the reactionto form said UCl is rapidly and completelyefiected. U 6. The process as defined in claim 1 wherein said oxide .1of uranium which is reacted withv said carbontetrachloride is a materialselected from the group consisting of U02, U308, and V j 7. In theprocess comprising contacting. carbon tetra: chloride vapor with amaterial selected from the group v consisting of U0 U 0 and U0 at areaction temperature of 450 C., whereby uranium tetrachloridev and reaction gases including phosgene-are produced, condensing; v, theunreacted carbon tetrachloride vapor, whereby carbon 2 tetrachloride isseparated thereby dissolving some of the phosgene from the remainderofthereaction gases, and reconverting the liquid carbon tetrachlorideand dissolved. phosgene into vapor to be contacted again with theunreacted oxide of uranium, whereby the unreacted carbon tetrachlorideand some of the phosgene are recycled repeatedly and maintaining thetemperature at 450 C. until said material is substantially completelyconverted to crystalline uranium tetrachloride, the major portion of theproduct having a crystalline size between 10 and 60 mesh; theimprovement consisting of disposing said material in trays within thereaction zone to a depth of between 0.1 and 0.5 centimeter whereby thereaction is rapidly and completely efiected.

8. The method as defined in claim 1 wherein said oxide of uraniumcomprises U 9. The method as defined in claim 1 wherein said oxide ofuranium comprises U0 10. The method as defined in claim 1 wherein saidoxide of uranium comprises U 0 References Cited in the file of thispatent UNITED STATES PATENTS 1,179,394 Barton Apr. 18, 1 916 1,646,734Marden Oct. 25, 1927 2,401,543 Brallier June 4, 1946 OTHER REFERENCESChem. Abstracts, vol. 5, page 1036, Ed. Chauvenet,

10 Compt. rend., 152, 87-9.

oretical Chemistry, vol. 12, pages and 83 (1932).

1. IN THE PROCESS COMPRISING CONTACTING CARBON TETRACHLORIDE VAPOR WITHAN OXIDE OR URANIUM AT A REACTION TEMPERATURE WITHIN THE RANGE 425* TO475*C., WHEREBY URANIUM TETRACHLORIDE AND REACTION GASES INCLUDINGPHOSGENE ARE PRODUCED, CONDENSING THE UNREACTED CARBON TETRACHLORIDEVAPOR, WHEREBY CARBON TETRACHLORIDE IS SEPARATED THEREBY DISSOLVING SOMEOF THE PHOSGENE FROM THE REMAINDER OF THE REACTION GASES, ANDRECONVERTING THE LIQUID CARBON TETRACHLORIDE AND DISSOLVED PHOSGENE INTOVAPOR TO BE CONTACTED AGAIN WITH THE UNREACTED OXIDE OF URANIUM, WHEREBYTHE UNREACTED CARBON TETRACHLORIDE AND SOME OF THE PHOSGENE ARE RECYCLEDREPEATEDLY AND MAINTAINING THE TEMPERATURE WITHIN SAID RANGE UNTIL THEOXIDE IS SUBSTANTIALLY COMPLETELY CONVERTED TO CRYSTALLINE URANIUMTETRACHLORIDE,THE MAJOR PORTION OF THE PRODUCT HAVING A CRYSTALLINE SIZEBETWEEN 10 AND 60 MESH; THE IMPROVEMENT CONSISTING OF DISPOSING THEOXIDE OF URANIUM CHARGE IN TRAYS WITHIN THE REACTION ZONE TO A DEPTH OFBETWEEN 0.1 AND 0.5 CENTIMETER WHEREBY THE REACTION BY RAPIDLY ANDCOMPLETELY EFFECTED.